“In these studies, Stribild demonstrated a robust clinical
profile, including sustained efficacy, safety and resistance
results over two years of treatment,” said Jürgen
Rockstroh, MD, Professor of Medicine, University of Bonn, Germany
and a lead investigator for Study 103. “Stribild was also
associated with a lower incidence of certain central nervous system
side effects compared to Atripla, and had a favorable triglycerides
profile versus the atazanavir-based regimen.”

Stribild combines four compounds in one daily tablet:
elvitegravir, an integrase inhibitor; cobicistat, a
pharmacoenhancing agent; emtricitabine and tenofovir disoproxil
fumarate. The regimen was approved by the U.S. Food and Drug
Administration (FDA) on August 27, 2012 for use by
treatment-naïve HIV-positive adults based on 48-week results
from Studies 102 and 103. A marketing application for Stribild is
currently under review in the European Union.

Study 102 found that at 96 weeks of treatment, 84 percent of
Stribild patients (n=293/348) and 82 percent of Atripla patients
(n=287/352) achieved HIV RNA (viral load) < 50 copies/mL, based
on the FDA snapshot algorithm (95 percent CI for the difference:
-2.9 to +8.3 percent for Stribild vs. Atripla; predefined criterion
for non-inferiority was a lower bound of a two sided 95 percent CI
of -12 percent).

Similarly, results from Study 103 show that 83 percent of
Stribild patients (n=294/353) and 82 percent of patients receiving
the atazanavir-based regimen (n=292/355) achieved HIV RNA < 50
copies/mL, based on the FDA snapshot algorithm (95 percent CI for
the difference: -4.5 to +6.7 percent for Stribild vs. the
atazanavir-based regimen; predefined criterion for non-inferiority
was a lower bound of a two sided 95 percent CI of -12 percent).

In both Studies 102 and 103, rates of discontinuation due to
adverse events were similar across all treatment groups (5 percent
for Stribild in each study, 7 percent for Atripla and 6 percent for
the atazanavir-based regimen). The most common adverse events
occurring in at least 10 percent of Stribild patients in Study 102
were diarrhea, nausea, upper respiratory infection, headache,
abnormal dreams, fatigue, depression and insomnia; in Study 103,
they were diarrhea, nausea, upper respiratory infection, headache,
nasopharyngitis, depression, back pain and fatigue. In Study 102,
there were consistently higher reports at each study visit through
96 weeks of abnormal dreams and dizziness in the Atripla arm, with
14 percent and 4 percent of patients experiencing abnormal dreams
and dizziness, respectively, on the Atripla arm vs. 8 percent and 1
percent, respectively on the Stribild arm at 96 weeks. Similarly,
in Study 103, reports of diarrhea were consistently higher through
96 weeks of treatment on the atazanavir-based arm compared to
Stribild, with 4 percent of Stribild patients vs. 9 percent of
patients on an atazanavir-based regimen experiencing this problem
at 96 weeks.

In September 2012, Stribild was added to U.S. Department of
Health and Human Services (DHHS) guidelines as an
“alternative” treatment regimen for patients new to HIV
therapy. Atripla and ritonavir-boosted atazanavir plus Truvada are
both listed as “preferred” first-line regimens in the
guidelines. Stribild has a Boxed Warning of lactic acidosis/severe
hepatomegaly with steatosis and post treatment acute exacerbation
of hepatitis B; see below for important safety information.

Five percent of Stribild patients and 7 percent of Atripla
patients discontinued treatment due to adverse events. The most
common adverse events leading to treatment discontinuation among
patients taking Stribild were renal events, depression and fatigue.
Between 48 and 96 weeks of treatment, two Stribild patients
discontinued due to serum creatinine increase without features of
proximal renal tubulopathy, and both patients improved after
treatment discontinuation.

At baseline, patients in the Stribild arm had a median HIV RNA
of 4.88 log10 copies/mL and mean CD4 cell count of 364
cells/mm3. Patients in the atazanavir-based arm had a
median HIV RNA of 4.86 log10 copies/mL and mean CD4 cell
count of 375 cells/mm3. Across both arms, 41 percent of
patients had HIV RNA > 100,000 copies/mL and 13 percent had CD4
counts ‰¤ to 200 cells/mm3.

At 96 weeks, patients in both arms experienced similar increases
in CD4 cell counts (mean increase of 256 cells/mm3 for
Stribild and 261 cells/ mm3 for the atazanavir-based
regimen). The virologic failure rate was 7 percent for both
treatment regimens. Five percent of Stribild patients and 6 percent
of patients on the atazanavir-based regimen discontinued treatment
due to adverse events. The most common adverse events leading to
treatment discontinuation among patients taking Stribild were renal
events, diarrhea, pyrexia, nausea, vomiting and fatigue. Between 48
and 96 weeks of treatment, one Stribild patient and one patient in
the atazanavir-based regimen discontinued due to serum creatinine
increase without features of proximal renal tubulopathy, and both
patients improved after treatment discontinuation.

Ocular icterus (associated with elevated bilirubin levels) was
less common among Stribild patients (less than 1 percent) compared
to patients taking the atazanavir-based regimen (14 percent).

Median changes from baseline in total cholesterol, HDL and LDL
at 96 weeks, were, respectively, +14, +6 and +14 mg/dL for
Stribild, and +8, +5 and +11 mg/dL for the atazanavir-based regimen
(total cholesterol, p=0.046; HDL, p=0.24; LDL, p=0.32). The median
change in triglycerides was +5 mg/dL for Stribild and +16 mg/dL for
the atazanavir-based regimen (p=0.012).

Studies 102 and 103 are ongoing in a blinded fashion. After week
192, patients will continue to take their blinded study drug until
treatment assignments have been unblinded, at which point all
subjects will be given the option to participate in an open-label
rollover extension and receive Stribild. Additional information
about the study can be found at
www.clinicaltrials.gov.

About Stribild

Stribild contains four Gilead compounds in a complete
once-daily, single tablet regimen: elvitegravir 150 mg; cobicistat
150 mg; emtricitabine 200 mg; and tenofovir disoproxil fumarate 300
mg. Stribild is indicated in the United States as a complete
regimen for the treatment of HIV-1 infection in adults who are
antiretroviral treatment-naïve. A Marketing Authorisation
Application (MAA) for the regimen was validated for review by the
European Medicines Agency (EMA) on December 20, 2011. Stribild does
not cure HIV-1 infection.

Elvitegravir is a member of the integrase inhibitor class of
antiretroviral compounds. Integrase inhibitors interfere with HIV
replication by blocking the ability of the virus to integrate into
the genetic material of human cells. Elvitegravir was licensed by
Gilead from Japan Tobacco Inc. (JT) in March 2005. Under the terms
of Gilead's agreement with JT, Gilead has exclusive rights to
develop and commercialize elvitegravir in all countries of the
world, excluding Japan, where JT retains rights. Gilead submitted a
New Drug Application (NDA) to FDA for elvitegravir as a standalone
agent on June 27, 2012, and the agency has set a target action date
under the Prescription Drug User Fee Act (PDUFA) of April 27, 2013.
An MAA for elvitegravir in the EU was validated for review by EMA
on June 18, 2012.

Cobicistat is Gilead's proprietary potent mechanism-based
inhibitor of cytochrome P450 3A (CYP3A), an enzyme that metabolizes
drugs in the body. Unlike ritonavir, cobicistat acts only as a
pharmacoenhancing or “boosting” agent and has no
antiviral activity. Gilead submitted an NDA to FDA for cobicistat
as a standalone agent on June 28, 2012, and a PDUFA date of April
28, 2013 has been set. An MAA for cobicistat in the EU was
validated for review by EMA on May 22, 2012.

Elvitegravir and cobicistat as standalone agents are
investigational products and their safety and efficacy have not yet
been established.

Lactic acidosis and severe
hepatomegaly with steatosis, including fatal cases, have been
reported with the use of nucleoside analogs, including tenofovir
disoproxil fumarate (“tenofovir DF”), a component of
Stribild, in combination with other antiretrovirals.

Stribild is not approved for the
treatment of chronic hepatitis B virus (HBV) infection and the
safety and efficacy of Stribild have not been established in
patients coinfected with HBV and HIV-1. Severe acute exacerbations
of hepatitis B have been reported in patients who are coinfected
with HBV and HIV-1 and have discontinued Emtriva or Viread, which
are components of Stribild. Hepatic function should be monitored
closely with both clinical and laboratory follow-up for at least
several months in patients who are coinfected with HIV-1 and HBV
and discontinue Stribild. If appropriate, initiation of
anti-hepatitis B therapy may be warranted.

Contraindications

Coadministration: Do not use
with drugs highly dependent on CYP3A for clearance and for which
elevated plasma concentrations are associated with serious and/or
life-threatening events. Do not use with drugs that strongly induce
CYP3A as this may lead to a loss of virologic response and possible
resistance to Stribild. Use with the following drugs is
contraindicated: alfuzosin, rifampin, dihydroergotamine,
ergotamine, methylergonovine, cisapride, lovastatin, simvastatin,
pimozide, sildenafil for pulmonary arterial hypertension,
triazolam, oral midazolam, and St. John's wort.

Warnings and Precautions

New onset or worsening renal
impairment: Cases of acute renal failure and Fanconi syndrome
have been reported with the use of tenofovir DF and Stribild.
Monitor estimated creatinine clearance (CrCl), urine glucose, and
urine protein in all patients prior to initiating and during
therapy; additionally monitor serum phosphorus in patients with or
at risk for renal impairment. Cobicistat may cause modest increases
in serum creatinine and modest declines in CrCl without affecting
renal glomerular function; patients with an increase in serum
creatinine greater than 0.4 mg/dL from baseline should be closely
monitored for renal safety. Do not initiate Stribild in patients
with CrCl below 70 mL/min. Discontinue Stribild if CrCl declines
below 50 mL/min. Avoid concurrent or recent use with a nephrotoxic
agent.

Use with other antiretroviral
products: Stribild is a complete regimen for the treatment of
HIV-1 infection. Do not coadminister with other antiretroviral
products, including products containing any of the same active
components; products containing lamivudine; products containing
ritonavir; or with adefovir dipivoxil.

Decreases in bone mineral density
(BMD) and cases of osteomalacia have been seen in patients
treated with tenofovir DF. Consider monitoring BMD in patients with
a history of pathologic fracture or risk factors for bone
loss.

Fat redistribution and
accumulation have been observed in patients receiving
antiretroviral therapy.

Immune reconstitution syndrome,
including the occurrence of autoimmune disorders with variable time
to onset, has been reported.

CYP3A substrates: Stribild can
alter the concentration of drugs metabolized by CYP3A or CYP2D6. Do
not use with drugs highly dependent on these factors for clearance
and for which elevated plasma concentrations are associated with
serious and/or life-threatening adverse events.

CYP3A inducers: Drugs that
induce CYP3A can decrease the concentrations of components of
Stribild. Do not use with drugs that strongly induce CYP3A as this
may lead to loss of virologic response and possible resistance to
Stribild.

Prescribing information: Consult
the full prescribing information for Stribild for more information
on potentially significant drug interactions, including clinical
comments.

Dosage and Administration

Adult dosage: One tablet taken
orally once daily with food.

Renal impairment: Do not
initiate in patients with CrCl below 70 mL/min. Discontinue in
patients with CrCl below 50 mL/min.

Hepatic impairment: Not
recommended in patients with severe hepatic impairment.

Pregnancy and Breastfeeding

Pregnancy Category B: There are
no adequate and well-controlled studies in pregnant women. Use
during pregnancy only if the potential benefit justifies the
potential risk. An Antiretroviral Pregnancy Registry has been
established.

Breastfeeding: Emtricitabine and
tenofovir have been detected in human milk. Because of both the
potential for HIV transmission and the potential for serious
adverse reactions in nursing infants, mothers should be instructed
not to breastfeed.

About Gilead Sciences

Gilead Sciences is a biopharmaceutical company that discovers,
develops and commercializes innovative therapeutics in areas of
unmet medical need. The company's mission is to advance the care of
patients suffering from life-threatening diseases worldwide.
Headquartered in Foster City, California, Gilead has operations in
North America, Europe and Asia Pacific.

Forward-Looking
Statement

This press release includes forward-looking statements within
the meaning of the Private Securities Litigation Reform Act of 1995
that are subject to risks, uncertainties and other factors,
including the risk that healthcare providers may not recognize the
benefits of starting patients new to therapy on Stribild. As
Stribild is used over longer periods of time by many patients with
underlying health problems taking numerous other medicines, Gilead
may find new issues such as safety, resistance or drug interaction
issues, which may require it to provide additional warnings or
contraindications on the label or narrow Stribild's approved
indication, each of which could reduce the market acceptance of
Stribild. In addition, regulatory authorities including the
European Medicines Agency may not approve marketing applications
for Stribild, elvitegravir and/or cobicistat in the timelines
anticipated or at all. Further, even if marketing approval is
granted for any of these products, there may be significant
limitations on their use. These risks, uncertainties and other
factors could cause actual results to differ materially from those
referred to in the forward-looking statements. The reader is
cautioned not to rely on these forward-looking statements. These
and other risks are described in detail in Gilead's Quarterly
Report on Form 10-Q for the quarter ended September 30, 2012, as
filed with the U.S. Securities and Exchange Commission. All
forward-looking statements are based on information currently
available to Gilead, and Gilead assumes no obligation to update any
such forward-looking statements.

U.S. full prescribing information for Stribild is available
atwww.Stribild.com.U.S. full prescribing information for Atripla is available
atwww.Atripla.com.U.S. full prescribing information for Truvada is available
atwww.Truvada.com.EU Summary of Product Characteristics for Atripla and Truvada is
available atwww.ema.europa.eu

Stribild is a trademark of Gilead Sciences, Inc.Truvada is a registered trademark of Gilead Sciences,
Inc.Atripla is a registered trademark of Bristol-Myers Squibb &
Gilead Sciences, LLC.

For more information on Gilead Sciences, please visit the
company's website atwww.gilead.com, follow Gilead on Twitter
(@GileadSciences) or call Gilead Public Affairs at 1-800-GILEAD-5
or 1-650-574-3000.

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